11-11-2016, 08:14 AM
Hi and welcome,
Hmmmm. Does seem a bit odd that the voltage feed point is the same for the two 24A rf tubes and the 71A's yet they are significant lower in voltage.
If you measure the voltage from the chassis (-) to the grid pin (+)(#3)how much do you have? Should see about -50vdc. Without that voltage the the plates of the 71A's are going to draw excessive current and cause a voltage drop across the output transformer's primary.
If the -50v checks out ok then connect your meter to measure the dc plate voltage on one of the 71A tube. Remove one of the 71A's. Does the voltage go up to it's normal 200v or so? Insert it back in and do like wise with the other 71A. If the voltage does rise up then your 71A is suspect.
Hmmmm. Does seem a bit odd that the voltage feed point is the same for the two 24A rf tubes and the 71A's yet they are significant lower in voltage.
If you measure the voltage from the chassis (-) to the grid pin (+)(#3)how much do you have? Should see about -50vdc. Without that voltage the the plates of the 71A's are going to draw excessive current and cause a voltage drop across the output transformer's primary.
If the -50v checks out ok then connect your meter to measure the dc plate voltage on one of the 71A tube. Remove one of the 71A's. Does the voltage go up to it's normal 200v or so? Insert it back in and do like wise with the other 71A. If the voltage does rise up then your 71A is suspect.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got it!
Terry
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